I've put the HTML tag on Page Properties -> Metadata -> HTML for head and uploaded the site again to FTP host but when I go back to the Google Webmaster / Search Control it says verification failed. I don't understand what could be the problem. Can anyone help?

It may take several days if not weeks, before you get results on google webmaster. I recommend not to panic. What exactly should be the result of the SEARCH CONTROL? On one of my own websites it took weeks, although it is a well known shopsystem behind with lots of proper SEO but exactly this one took a long time.